PLATE m, 



Pago 

 Fig. I a - z, & 2 a - d. Rhynchonella pyramidata. 229 



I a - d. Young individuals of this species. 



1 e - z. Illustrations of the varying forms of this species, from those of medium size to the 



largest and most gibhous forms that have been observed. 



2 a. A cast of the ventral valve of this species, showing the muscular impression smaller than 



in R. nucleolata, Plate xxxi, fig. 2 x. 



2 6. A cast of the dorsal valve of the same species. 



2 c. Interior of the ventral valve, which partially preserves the form of the muscular imprint 



